﻿674 ME. H. BURT ON THE DENUDATION OE [Nov. I9IO, 



trace, in the present consequent and obsequent streams, two former 

 consequents : (a) from the Devil's Punch Bowl (Hindhead) past 

 Elstead and Cutmill, and so over the Hog's Back near Shoelands 

 (1 mile east of Seale); and (b) from Gibbet Hill (Hindhead) by- 

 way of Peperharrow and Puttenham to Wanborough, etc. (see map, 

 fig. 5, p. 666). 



I have endeavoured in fig. 5 to indicate the probable distribution 

 of Chalk on the plain. Such an attempt is beset with so many 

 sources of error that no accuracy of detail is to be hoped for ; but, 

 even if wrong, in many respects the diagram will serve to illustrate 

 certain broad features which, if planation really occurred, must 

 have had their effects on river-development. 



If we take Section 73 of the Geological Survey and reconstruct a 

 plain running from the summit of Hindhead to the hypothetical 

 line shown in fig. 1 (that is, 660 feet at Puttenham), we find the 

 Chalk stretching away in a continuous sheet as far south as 

 Thursley. I do not think, however, that the details of this section 

 can be altogether correct. In the first place, the thickness assigned 

 to the Selbornian Beds (Gault and Upper Greensand) is probably 

 far too small, and no allowance is made for the overthrusting and 

 compression of the Chalk (29, p. 432). In the next place, Crooks- 

 bury Hill, a mile and a half to the west of this section, reaches 

 534 feet O.D., and consists wholly of Lower Greensand ; and, 

 assuming that it presents the top of the Folkestone Beds, we must 

 still add about 250 feet for the Selbornian (9, vol. i, p. 92), 

 bringing the base of the Chalk to 784 feet. The theoretical level 

 of the plain, allowing a gradient of 30 feet per mile, is about 

 700 feet, so that there was probably an area from which the Chalk 

 was absent ; and, since there is a general dip towards the west, the 

 Lower Cretaceous rocks must a fortiori have been exposed farther 

 east. I am led, in fact, to believe that a belt of the latter rocks 

 extended all the way along the crest of the anticline from Guildford 

 to the Waverley Valley, and perhaps beyond, while a second belt 

 of Chalk, planed off very thin, occupied tbe syncline to the south. 

 The effect of this peculiar structure on the rivers can only be con- 

 jectured. The position which I have ascribed in fig. 5 to one of 

 the early consequents suggests that it may possibly have been con- 

 cerned with the production of some of the chert-bearing gravels 

 farther north (Fox Hills, Chobham Bidges,etc.) ; but, although this 

 would simplify the explanation of certain peculiar gravels about 

 Windlesham (see 13, p. 36), there is no real evidence in favour 

 of such a view. The Godalming Biver may have arisen in the 

 Lower Greensand at an early stage, south of its present position, 

 and followed the retreat of the Chalk northwards ; and some of 

 the early drifts around Thursley may be relics of this period. The 

 streams traversing the northern belt of Lower Cretaceous rocks 

 would then be diminished in volume, and soon diverted into sub- 

 sequent courses, one running from Puttenham past Seale to the 

 Aldershot gap (Seale stream) and the other eastwards from Compton 

 to Shalford. The latter still survives, but the former, having a 



